peterson



May 28, 1957 Filed Dec. 3 1951 F. c. PETERSON 2,793,750

METHOD AND MEANS FOR CONCENTRATING VALUABLE COMPONENTS OF PLACER GRAVEL 2 Sheets-Sheet 1 INVENTOR.

FkA Am G P575230 WMW ATTOENEYS May 28, 1957 F. c. PETERSON METHOD AND MEANS FOR CONCENTRATING VALUABLE COMPONENTS OF PLACER GRAVEL 2 Sheets-Sheet 2 Filed Dec. 3, 1951 INVENTOR. FEA NK CPereesoN ATTOR NEYS United States Patent Ofiti? 2,793,750 Patented May 28, 1 957 METHOD AND MEANS FOR CONCENTRATING VALUABLE COMPONENTS OF PLACER GRAVEL Frank C. Peterson, Oroville, Calif.

' Application December 3, 1951, Serial No. 259,643

3 Claims. (Cl. 209-457) This invention relates to new and useful improvements in apparatus and method for concentrating minerals and constitutes an improvement over my Patent No. 2,311,- 414, issued February 16, 1943. The general method of operation of jig concentrators of the type to which this invention relates is set forth in said patent. The instant.

invention relates to improved means and methods for concentrating the material being handled by shot bed agitation.

One improvement of the present invention over that disclosed in my said prior patent relates to the mechanism for creating pulsations of the undercurrent flow. This is accomplished by means of an oscillating transverse wall pivotally mounted in the hutch, which is caused to vibrate to form pulsation of the undercurrent water. Said wall is caused to vibrate within the range of 1800-2200 vibrations per minute, with best results obtained at about 1950 vibrations per minute, when used for example, in the separation of valuable components, such as gold, from a typical California placer gravel. For other types of materials, such as in the separation of coal from slate,

different frequencies may be desirable.

Another improvement resides in the fact that the mechanism for vibrating said wall is located externally of the hutch, where it is secure and dry and readily accessible and removable.

Still another advantage of this invention is the fact that a continuous undercurrent of water is introduced into the hutch, the quantity of water being greater at all times than that quantity displaced by vibration of the transverse wall. Another feature of the invention resides in the fact that said undercurrent of water is introduced through a port in the side wall of the hutch past which the vibrating transverse wall swings. As said wall swings past the opening, alternately a greater and lesser proportion of the undercurrent water is directed to each side of the hutch. Thus as the wall displaces the water in one side of the hutch and pushes it upward through the shot bed, undercurrent water is directed in back of the wall andprevents suction in the other side of the bed. The elimination of suction is one of the principal advantages of the instant invention in that in prior hutches suction tends to compact and stratify the material in and above the shot bed, whereas in the instant invention the material in and above the shot bed is soft, loose and permeable. This permits even very fine and flaky particles of valuable material to be drawn down into the hutch.

The instant invention reduces the height of the concentrator thereby eliminating the requirement of reelevating the concentrate from the rougher to the cleaner and amalgamator.

The resultant of the foregoing objects of the invention is the provision of a simple, eificient and durable device which requires a minimum of power for operation.

The method whereby material is concentrated presents important differences over previously practiced, in that the bed above the shot bed is soft and permeable rather than hard and stratified. This effect is produced by reason of the fact that the method herein employed contemplates a constant undercurrent flow which is greater than the pulsations produced by the vibrating wall, which, in turn, continuously works the shot bed and agitates the contents, and the elimination of suction through the shot bed. Practice of the method to obtain optimum results depends upon the following variables: Quantity of undercurrent water; depth of shot bed; frequency of vibrations of transverse wall; and amplitude of ospillation of transverse wall.

Other objects of the present invention will become apparent upon reading the following specification and referring to the accompanying drawings in which similar characters of reference represent corresponding parts.

in each of the several views.

Fig. 1 is an end view of the concentrator as viewed from the up-stream side and showing twin concentrators.

Fig. 2 is a longitudinal vertical section taken substantially along the line 2-2 of Fig. 1.

Fig. 3 is a transverse vertical mid-section taken substantially along the line 33 of Fig. 2.

The instant invention relates to concentration of minerals by a pulsating jig. One'such jig is shown in my Patent 2,311,414, issued February 16, 1943. The material to be concentrated, which is usually a low grade ore, is carried down in a sluice box in a stream of water.

The bottom of the sluice box is cut away and below the opening a jig or hutch is installed. Said jig is provided with a shot bed ofsmall steel shot immediately below the sluice, said shot bed resting upon-a screen or grid. A pulsating undercurrent of water is forced upward through the screen and up through the shot, said undercurrent serving t-o'agitate and work the shot and the ore which rests upon it, the resultant effect being that the heavier and valuable components of the material being handled work down to the bottom of the shot bed and pass down through the screen or grid, where they may be recovered. After passing through the hutch, 'recovery of the high-value ore may be accomplished by means of an amalgamator and concentrate discharge control such as that shown in my Patent No. 2,289,678, issued July 14, 1942.

The present invention relates to certain improvements over my prior patents and means and methods employed by others.

Accordingly, as shown in the accompanying drawings, there is provided a downwardly inclined sluice consisting of an inclined bottom 10 and substantially vertical sides 11, said sluice providing a conduit for the material and water to be classified. The gradient of the sluice in the vicinity of the hutch is preferably 1% inches per foot. The bottom of the sluice is cut away to provide an opening 12 immediately above the hutch. Immediately downstream of said opening a stop-gate 13 extends transversely across the sluice. The elevation of said stopgate 13 is the same as that of sluice bottom at the upstream side of opening 12, thereby eliminating all grade. The eflect of said stop-gate 13 is to form a bed 14 of live sand and water upstream thereof. The function of the hutch is to withdraw from said bed of sand and water the heavier particles of material tobe recovered.

Open-top casing 16 formed of steel plate is installed beneath the sluice, the upper part of said casing 16 having vertical sides 17 which are rectangular in horizontal cross-section and surround the opening 12 in the sluice. About twelve inches below the top ofsaid casing the sides 18 of casing 16 slope inwardly at about a 45 angle, and at the bottom, where said sides converge, a discharge port 19 is provided. Said discharge port 19 is connected to an amalgamatorand concentrate dischargecontrol such as that of my said Patent 2,289,618.

A screen 21 is installed below opening 12, the gradient of said screen being the same as the sluice. Above screen or grid 21 is a bed 22 of steel shot of a diameter between A and /2 inch, screen 21 being time enough to prevent passage of the shot therethrough. Nuggets of material lodge on said screen 21, but the bulk of the valuable components of material pass'through and into the hutch. Preferably the space above screen 21 is divided into a plurality of compartments by transverse, vertical partitions 23, the tops 24 of which are along a plane having the same. gradient as the bottom 10 of the sluice.

At least one centrally disposed longitudinally extending vertical partition 26 may be provided in shot bed 22.

Partitions 23 and 26 serve to define a;series'of.rifiies which improves classification of the material handled. The shot bed 22 in each partition is thus trapezoidal when viewed in cross-section. Valuable components tend to pass into the bed at the:upstream edge of each compartment, by reason of said partitions functioning .as a raffle box. It will also be apparent 'thatthe upstream portion of each section of theshot bed will collect the bulk of the valuable components and that this part of the shot bed is thinner than at the downstream portion, which arrangement facilitates rapid concentration. It may also be pointed out that the upstream sections of the shot bed handle the bulk of the heavy particles, making the downstream sections with their overlying thicker bed 14 available for concentration of the smaller heavy particles.

Below screen 21 and extending transversely across and within the hutch is a plurality of water baffies 27 which assist in supporting screen 21 and further serve to make the passage of undercurrent through the shot bed more uniform and vertical. Said baflies 27 are welded to the interior side walls 16 of the hutch. Said 'bafiies 27 are disposed so as to direct the flow of undercurrent water uniformly through the shot bed.

The pulsation of the undercurrent is accomplished by a transverse steel plate wall 31 which extends across the middle of the hutch, said wall being suspended from transverse torsion hinge 32 disposed immediately below screen 21, which hinge provides a pivot so that wall 31 may oscillate through an amplitude of about one inch at its lower edge 33, which lower edge is slightly above the bottom of the hutch. This arrangement permits wall 31 to vibrate freely, the hinge requirin'g'no lubrication and a minimum of maintenance and having along life.

At about the center of the upstream surface of wall 31 there is a second torsion hinge 41, and to said hinge is attached connecting rod 42 which extends upwardly at an angle until it passes through upstream vertical. wall 17 of casing 16. A rubber bellows 43 is connected to casing 16 and to rod 42 so as to form a water-tight seal around rod 42.

The upper end of rod 42 is fixed toeccentric collar 44 which passes around a variable stroke eccentric 46 turned by transverse shaft 47 which is driven by electric motor 48 by means of 'belt 49 and pulleys 51 and 52. Observation conducted upon typical California placer gravel had disclosed that the operation of the jig is affected materially by the frequency of vibration of the transverse wall 31. A number of different periods of vibration of increasing frequency produce superior classification results. The most practical range is between 1800 and 2200 vibrations per minute, and within this range 1950 vibrations has been found most advantageous. Frequencies above and below this range which result in superior classification are less practical because of problems in vibrating the transverse wall effectively.

The undercurrent of water is provided through pipe 56 which communicates with hutch through port 57 in side wall 18 near the bottom of they hutch, said port 57 being centered so that water is admitted equally oneither side of wall 31. The quantity of water admitted through port 57 is at all'times greater thanthe amount of water displaced by movement ofwall 31.

As shown particularly in Fig. 2, port 57 is positioned in one of the longitudinal side walls 18 at the center of the hutch and also at the center of the motion of wall 31. Thus when wall 31 is at dead center the flow "out through port 57 is divided equally between the two ends of the hutch, but as wall 31 moves toward either end of its stroke the flow through port 57 is divided unequally, the greater quantity going to the side opposite that toward which wall 31 has moved. The efiect of this arrangement is that as wall 31 moves toward one end of its stroke the space behind the wall is filled with water, thereby eliminating suction. In prior art hutches, suction of the moving element of the jig tended to compact and stratify the material within and above the shot bed, with the result that areas of the bed were rendered totally ineffective and, further, the entire bed was reduced in efficiency in that the very light flaky particles were not drawn down through the screen. In some types of ore, loss of the light flaky particles is extremely important because they represent an appreciable percentage of the total valuable components. Light, finely-divided particles having a relatively large surface area tend to travel high in the gangue material. In the present invention the sand bed 14 elevated above shot bed '22 acts to entrap values which would otherwise escape by not having contacted the shot bed.

. As shown particularly in Fig. 1, two hutches A and B may be arranged side by side across the sluice, each concentrating half of the material passing along the sluice. Such arrangement makes possible the driving of both vibrating walls 31 by a single eccentric shaft 47 and if the eccentrics 46 are disposed on opposite sides of the center of shaft 47, considerable economy in operation may be effected. Further, this arrangement reduces mechanical vibrations which is important in that mechanical vibration results in a sifting action which opposes the hydrostatic concentration principles upon which the hutch operates. This arrangement, plus other features of the invention, eliminate or materially reduce mechanical vibrations, which produce a sifting action, as distinguished from the hydrostatic pulsations which result in concentration. Pulley 52 is made heavy and an additional fly wheel may be employed on shaft47 to dampen out vibrations.

In operation, water and material to be concentrated preferably in a ratio of three to one respectively and with a maximum ratio of about five to one is caused to flow down the sluice. The volume of undercurrent water is about ten gallons per minute per square foot of screen area, but may vary depending upon the specific gravity of the material being handled and the dilution.

Stop-gate 13 causes a wedge-shaped bed 14 of sand and water, which is soft and permeable, to be maintained at all times. The heavier particles work to the bottom of this bed and thence are worked in with the shot bed 22 and thence pass down through the screen 21.

A constant undercurrent of water passes into the hutch through port 57 and this plus the pulsations produced by transverse vibrating wall 31 causes a lifting effect through shot bed 22which permits the heavy particles of material to work downwardly. The pulsation of the undercurrent is caused by wall 31 which vibrates about transverse torsion shaft 32 as a pivot and thus causes an augmented undercurrent first on one end and then the other of the shot bed. Since the amount of water introduced through port 57 is greater than the water displaced by vibration of wall 31, the -material in shot bed '22 is not com pacted and stratified, but on the contrary is relatively loose. The swinging of wall 31 across port 5'7 fills the space behind the Wall and prevents suction through the shot bed, as has been described. By this arrangement a more rapid classification is accomplished.

After passing down through screen 21, the'material drops to the bottom of the hutch anddischarges through port 19. Port 19 is preferably connected to a discharge control and amalgamator such as that described in my said Patent 2,289,678.

It will be seen that the operation of the concentrator depends upon a number of variables, primarily depending upon the type of material being handled and the proportion of valuable components therein. The variables at the control of the operator include the depth of the shot bed, quantity of flow of undercurrent water, and amplitude and frequency of vibration of the transverse wall. The character of the material being handled and the proportion of water and solid in said material is generally determined by factors not under the immediate control of the operator, and hence the variable factors must be adjusted for optimum recovery of valuable components.

I claim:

1. A jig concentrator comprising in combination, an opentop downwardly converging casing, a discharge port adjacent the bottom of said casing, a screen extending across said casing adjacent the top thereof, a shot bed above said screen, a transverse wall extending across said casing and substantially dividing the area below said screen into two compartments, a hinge immediately below said screen for pivotally mounting the top of said wall within and adjacent the top of said casing for oscillatory motion, the lower edge of said wall being free for swinging movement, power means for imparting oscillatory motion to said wall, and an undercurrent water inlet port in said casing below said screen located remote from said hinge and further located so that said wall swings across said inlet port as said wall is oscillated, the amplitude of swinging movement of said wall being substantially equal on either side of said inlet port.

2. A jig concentrator comprising in combination, an opentop downwardly converging casing, a. discharge port adjacent the bottom of said casing, a screen extending across said casing adjacent the top thereof, a shot bed above said screen, a transverse wall extending across said casing and substantially dividing the area below said screen into two compartments, a hinge immediately below said screen for pivotally mounting the top of said Wall within said casing for oscillatory motion, the lower edge of said wall being free for swinging movement, means for imparting an oscillatory motion to said wall, a port in said casing located so that said wall swings across said port, said port being disposed equally on either side of the mid-position of said wall, and means for supplying a continuous undercurrent of water through said port.

3. A method of concentrating valuable components from gravel in a jig comprising the steps of passing said gravel down a sluice with water in a ratio of less than five parts water to one part solid: forming and maintaining a loose, soft, permeable bed of fine sand; forming and maintaining a loose, permeable bed of shot and gravel under said sand bed; maintaining an undercurrent of water upwardly through said shot bed which is at all times and at all locations of said bed a positive, upward flow; and pulsating said undercurrent, the amount of undercurrent water being at all times greater than the amount of water displaced in pulsation.

References Cited in the file of this patent UNITED STATES PATENTS 1,058,349 Bookwalter Apr. 8, 1913 1,144,494 Neill June 29, 1915 1,173,465 Steel Feb. 29, 1916 1,243,395 Fellow Oct. 16, 1917 1,378,521 Brindley May 17, 1921 2,070,069 Ruoss Feb. 9, 1937 2,238,338 Moir Apr. 15, 1941 2,311,414 Peterson Feb. 16, 1943 2,328,402 Tuthill Aug. 31, 1943 2,586,574 Smith Feb. 19, 1952 FOREIGN PATENTS 447,290 France Dec. 28, 1912 

